Things fall apart: why do the ecosystems we depend on collapse?

David Lindenmayer, Australian National University

People collapse, buildings collapse, economies collapse and even entire human civilizations collapse. Collapse is also common in the natural world – animal populations and ecosystems collapse. These collapses have the greatest impact on us when they affect resources our industries depend on, leaving ecosystems in tatters and sometimes ruining local economies.

In a new paper, I look at two natural resource industries – fisheries and forestry – that are highly susceptible to collapse.

From the infamous 1980s collapse of the Canadian cod industry to the apparent imminent collapse of the Heyfield sawmill in southern Victoria, we can see a recurring pattern. And by getting better at predicting this pattern, we might be able to avoid collapse in the future.

The stages of collapse

In fisheries, collapse follows a familiar pathway, which has up to eight stages. In a 1993 report for the US Marine Mammal Commission on harvesting ocean resources, L.M. Talbot described these stages:

  1. fishers discover a new fishery, or a new method of harvesting an existing stock

  2. fishers develop the new resource with little or no regulation

  3. major fishing effort results in over-capitalisation of the equipment used to harvest the resource – the value of the fishery can sometimes even be less than the investment fishers made

  4. fishers develop the capacity to catch more fish than the fishery can sustain

  5. fishery becomes depleted and the number of fish caught begins to decline

  6. fishers intensify their efforts to catch fish to offset the decline in harvest

  7. intensive fishing continues as fishers attempt to recoup investments in over-capitalised equipment

  8. fishery is depleted to such levels that it is no longer economic for fishers to go fishing. At this stage the fishery is fully collapsed.

In some cases, regulators attempt to manage the fishery as fishers intensify their efforts. Examples include putting in place quotas and economic subsidies, or reducing the fishing capacity of the fleets.

However, these are often belated and ineffective. This is particularly so given uncertainty about the fishing resource, lack of information on the ecology of the target species, and the fact that an industry with vested interests will lobby hard to protect those interests.

Subsidies at these stages – such as tax breaks and/or fuel rebates – may mean that fishing becomes artificially profitable. Fishers may remain in the industry and continue to overinvest to obtain a greater share of a dwindling resource.

Many forestry industries around the world show similar stages.

Native forest harvesting in Australia is a highly capital-intensive industry. It uses heavy machinery that costs a lot to purchase, leading to high interest repayments. Such efficient harvesting may not only employ relatively few people, but also outstrip the amount of timber that can be sustainably harvested (like stage four in fisheries collapse).

Significant amounts of timber and pulpwood need to be processed continuously to pay the interest and other bills for equipment (stage seven).

Moreover, logging may continue even though it is highly uneconomic to do so (stage eight) and other industries that are damaged by logging (such as the water and tourism industries) are significantly more economically lucrative.

Why do industries overharvest?

Fisheries and forestry often allocate greater harvest limits than the ecosystem can produce without declining.

One key reason this happens is that fish or timber allocations often don’t account for losses from natural events.

For example, the mountain ash forests of Victoria rely on severe wildfires to regenerate. They are also extensively logged for paper and timber production.

Yet the organisation responsible for scheduling of logging in these forests (VicForests) does not account for losses due to fire when calculating how much timber can be harvested. Major fires in 2009 badly damaged more than 52,000 hectares of this forest. But environmental accounting analyses indicate there has been relatively little change in sustained yield allocation since these fires.

Yet, modelling suggests that, over 80 years, wildfire will damage 45% of the forest estate. This amount should therefore should not be included as timber available for logging.

Another driver of the problem of resource over-commitment can be gaming, where stock availability and direct employment are deliberately overstated. This may be to secure the status and influence of a given institution with government, or for other reasons such as leverage in negotiations over access to resources.

The autobiography of Julia Gillard, the former Australian prime minister, suggests this occurred during debates over the fate of forests in Tasmania, alleging that Forestry Tasmania overstated forest available for harvest. Forestry Tasmania denied these allegations.

What can we do?

Early intervention in fisheries and forestry industries can prevent ecosystem and industry collapse. We also need to better ways to assess resources, including accounting for losses of resources due to natural disturbances.

However, in some cases resources have been so heavily over-committed that industry collapse is virtually inevitable. For example, environmental accounting work in the wet forests of the Central Highlands of Victoria suggests very little sawlog resource is left as a result of many decades of overcutting and associated wildfire. Clearfell logging makes these forests more prone to particularly severe fires.

The collapse of the sawlog industry is highly likely, even if there is no fire. This is clear from the pleas from sawmills for access to further forest resources – even when such extra resources basically do not exist.

Now the industry needs to transition to plantations for paper production and for timber (82% of all sawn timber already comes from plantations in the state).

Alternative industries like tourism that employ far more people and contribute more to the economy must be fostered. There are many examples to draw on – New Zealand is one of many.

When governments know in advance about likely industry collapse, then it is incumbent upon them to intervene earlier and help foster transitions to new (and often more lucrative) industries. This ensures that workers can find jobs in new sectors, and the transition is less painful for the community and less costly for taxpayers. Failure to do this is unethical.

The closure of the Hazelwood power station in Victoria is a classic example of a lack of planning for industry transition. The need to close Hazelwood was discussed in formal reports by the former State Electricity Commission more than 25 years ago.

The need to transition the native forest industry to plantations is equally clear and must be done as a matter of urgency.

The Conversation

David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University

This article was originally published on The Conversation. Read the original article.


Rising extreme weather warns of ecosystem collapse: study

Alfredo Huete, University of Technology Sydney and Xuanlong Ma, University of Technology Sydney

The world’s climate is already changing. Extreme weather events (floods, droughts, and heatwaves) are increasing as global temperatures rise. While we are starting to learn how these changes will affect people and individual species, we don’t yet know how ecosystems are likely to change.

Research published in Nature, using 14 years of NASA satellite data, shows eastern Australia’s drylands are among the most sensitive ecosystems to these extreme events, alongside tropical rainforests and mountains. Central Australia’s desert ecosystems are also vulnerable, but for different reasons.

As the world warms, this information can help us manage ecosystems and to anticipate irreversible changes or ecological collapse.

Maps created using satellite data to show which ecosystems are most sensitive to climate (orange) and least sensitive (green). Both could be worrying as the world warms.
Seddon et al.

Tipping points

Ecological theory tells us that as ecosystems become unhealthy, they approach critical thresholds (also referred to as tipping points). The more unhealthy they become, the quicker they respond to disturbances.

Ecosystems that cross a critical threshold are transformed into new states, often with losses in biodiversity, exotic species invasions, and sudden forest die-off events. For example, over the past 10 years, ecosystems in the western US have experienced large-scale tree deaths and native, black grama grasslands have been transformed to the exotic, South African Lehmann lovegrass.

Farms and crops can be thought of as agricultural ecosystems, and they are highly sensitive to variations in climate. This means they are very challenging to manage for sustainable livestock and crop production under such intensifying conditions of sudden good and bad periods.

As humans we show weakened resistance when we are sick, and we become more susceptible to external conditions. Similarly, slower than normal ecosystem responses to external changes may also be indicative of an unhealthy ecosystem.

Both of these measures, fast and slow, are early warning signs for ecosystem collapse.

Seeing ecosystems from space

But how do we know if an ecosystem is going to collapse? Space offers a unique vantage point. The new research uses data from NASA’s Moderate Resolution Imaging Spectroradiometer (or MODIS) satellites. The satellites, orbiting roughly 900 km above Earth’s surface, measure things like snow and ice, vegetation, and the oceans and atmosphere.

The satellites measure ecosystem “greenness”, which indicates how much an ecosystem is growing. This is not too different from a farmer visually interpreting cues of plant health based on colour, except that satellites can have the capability to analyse colour in parts of the spectrum beyond our sensing capabilities.

The researchers developed a “Vegetation Sensitivity Index”, which showed how ecosystems responded to changes in climate. They particularly looked at changes in temperature, cloud cover, and rainfall.

One nice aspect of this research is that it specifically shows which climate component has the biggest role in changing ecosystems. For example changes to alpine meadows were attributed to warming temperatures, while tropical rainforests were very sensitive to fluctuations in solar radiation (or cloud cover).

Australia’s dry ecosystems show dramatic changes between wet and dry. This is spinifex grassland during the dry. Spinifex covers around 20% of Australia’s land area.
James Cleverly, Author provided

Mulga woodland during a wet period.
James Cleverly, Author provided

Australia’s vulnerable ecosystems

Eastern Australia’s dry woodlands and semi-arid grasslands, according to the study, are some of the most sensitive ecosystems to climate change, alongside tropical rainforests and alpine regions. The main factor in Australia is water.

This is in line with our recent study conducted in southeast Australia since 2000, which shows sudden, abrupt shifts in ecosystem function over many semi-arid ecosystems. This demonstrated the vulnerability of eastern Australian ecosystems to climatic variability and future extreme climatic events.

The new study also found central Australia’s deserts and arid lands show unusually slow responses to climate variability, which is concerning. Slower responses may be an early warning that these ecosystems are approaching a critical threshold before collapsing.

But this might also be an adaptation to the extreme climate variability these ecosystems already experience. The vegetation “knows” that the good, rainy times don’t last and therefore they may not invest in new growth that will later become a burden when drought returns.

What does this mean for ecosystems?

This research isn’t the end of the story. Although satellite data are valuable, they can’t tell us exactly what are the causes or mechanisms of ecosystem change. To do that, we need information on the ground, and consistent data over long periods of time is hard to come by. One example is Australia’s Terrestrial Ecosystem Research Network, or TERN.

The next step is to attribute the reasons why some systems appear to be more sensitive than others and more importantly, predict where and when the critical transitions will occur.

When forests, grasslands, and other ecosystems approach their critical thresholds, their resistance is weakened and they become highly susceptible to insects, pests, disease, species invasions, and mortality. One way to help ecosystems cope may be to reduce pressures on the land, such as recreation, harvesting and grazing.

If ecosystems collapse, we can mitigate some of the damage by helping wildlife and minimising soil erosion and runoff following tree deaths. But the most important thing is recognising that each ecosystem will behave differently; some may collapse, but others will survive.

The Conversation

Alfredo Huete, Professor, Plant Functional Biology & Climate Change, University of Technology Sydney and Xuanlong Ma, Research Associate in Remote Sensing of Environment, University of Technology Sydney

This article was originally published on The Conversation. Read the original article.

Inskip beach collapse: just don’t call it a ‘sinkhole’

Stephen Fityus, University of Newcastle

As was widely reported in the media, at around 10pm last Saturday night, a “sinkhole” opened up at a beachfront campground on the Inskip peninsular.

The thing is, it almost certainly wasn’t a sinkhole.

Unanticipated ground collapses occur around the world from time to time, and these generally get labelled “sinkholes”, for want a more appropriate term. Yet “sinkhole” is poorly defined and often misused, generally referring to some type of geological phenomenon that causes localised ground surface collapse.

In its strict sense, a sinkhole occurs when there is movement of surface soil or rock downward to fill a cavity in the ground below it. Thankfully, open underground cavities are not so common in nature, and are limited to a few characteristic geological settings.

The classic manifestation of sinkholes is in karstic geological environments, such as the Nullabor Plains. These are where the percolation of groundwaters through limestones and dolomites over geological timescales causes them to dissolve, leading to the formation of underground cave systems.

Where the span of the caves becomes too great, or the overlying roof rocks are too thin to support themselves, these may collapse. This produces the stereotypical sinkholes such as those known from Guatemala, Florida, Louisiana, and parts of China.

Sinkholes can also arise from anthropogenic activity, such as mining and engineering works. Poorly backfilled or capped mine shafts may subside if the backfill collapses or is washed to deeper levels in the mine by inflowing water, such as occurred in the case of the Swansea “sinkhole” near Newcastle, New South Wales, in 2014.

Shallow tunnels can also collapse, leading to a hole or depression forming in the ground above. Small sinkholes can also occur above breaks in unpressurised wastewater pipes if soil from around the pipes is able to collapse into the pipe and be carried away with the flowing water.

Sandy straight

So how does any of this explain the Inskip beach “sinkhole”? Well, it doesn’t. And from the photographs and available geological information, it seems like the event at Inskip beach is not a sinkhole at all.

The Inskip beach area is not undermined, and not known for the occurrence of limestones in its bedrock. So its very unlikely that the missing sand has been swallowed into some deep hole in the sea floor.

To understand the likely reasons behind the Inskip event, it is necessary to understand the geological setting of the Inskip peninsular. For millions of years, the coastal river systems of New South Wales have generated vast quantities of clean quartz sand, which have been delivered to the ocean.

Some of this sand is pushed up to create some of the best sandy beaches in the world. Meanwhile, the excess (and there is a lot of it) is swept northward along the coast by ocean currents until it reaches a place where it can be deposited.

Through a complex combination of ocean current, ocean swell, coastal morphology and bathymetric factors, Fraser Island in Queensland – the largest sand island in the world – is the repository for much of this excess sand.

The situation is complicated by the Mary River, which discharges into the ocean at the same place. This means that Fraser Island is separated from the mainland by a channel, which allows the Mary River to discharge to the ocean, mainly northward through Hervey Bay.

The southern end of this channel, the “Great Sandy Straight”, forms an estuary at Tin Can Bay, which accommodates tidal flows inward and outward between the Inskip peninsular and Fraser Island. And this is the site of recent collapse event.

It might look like a sinkhole, but it’s something quite different.
AAP Image/Higgins Storm Chasing

Slippery sand

Tidal channels are dynamic environments, carrying sand backward and forward on a daily basis, depositing sand, and then scouring it out again when the channel becomes constricted. If sand is spilled into a pile, it forms a slope at a characteristic angle, referred to as the angle of repose.

If a slope is made any steeper than this, it is potentially unstable and prone to collapse. Sands deposited to form the submerged banks of the channel are flatter than, or equal to, the angle of repose and exist in a stable condition.

However, if the sandy banks of the channel are steepened through erosion in the bottom of the channel, then the over-steep submerged slope may become unstable, resulting in a submarine landslide. Such a slide, initiated at the toe of the slope, will effectively see the slope unravel, with slices of the slope progressively slumping into the space created by the slumping of the slice below.

This mechanism fits well with the situation at Inskip beach, both in terms of the geomorphological conditions and the reported characteristics of the beach collapse.

Will there be more events like this? At some time in the future, most likely. But when, where and how big are all questions that are difficult to quantify without site specific geotechnical and hydromorphological data. Coastal environments are dynamic, restless environments, and the risks of sudden changes are small, but ever-present.

The Conversation

Stephen Fityus, Professor in Geotechnical Engineering, University of Newcastle

This article was originally published on The Conversation. Read the original article.